Stainless Steel Heating Coil Tube — Oil Tank Thermal Exchange System (Coiltube)
Product Overview
The Stainless Steel Heating Coil Tube (hereinafter referred to as "Coiltube") is a precision-engineered tubular product manufactured by Wenzhou Jixing Metal Materials Co., Ltd., specifically designed for thermal energy transfer applications in industrial oil tank heating systems. This product is classified under the Coiled Tubing category and is engineered to facilitate efficient heat exchange between a heating medium (typically hot water or steam) and stored petroleum products or chemical fluids within storage tanks.
The Coiltube serves as a critical component in Oil Tank Heating Systems, where it is submerged within the tank to transfer thermal energy to the contained fluid, ensuring proper viscosity management, flowability, and operational readiness of the stored product. The design and material selection of this Coiltube are governed by rigorous standards for corrosion resistance, mechanical integrity, and long-term thermal performance in demanding industrial environments.
This product is particularly associated with advanced Leak Detection and Return Water Monitoring Technologies (泄漏回水检测工艺), which are integral to the operational safety and efficiency of oil tank heating installations. The integration of leak detection protocols ensures that any compromise in the coil tube's integrity is identified promptly, preventing environmental contamination and operational hazards.
Material Composition & Properties
Base Material
The Coiltube is fabricated from high-grade Stainless Steel, with the primary alloy options including:
- Austenitic Stainless Steel (奥氏体不锈钢) — Grades such as 304 (UNS S30400), 316 (UNS S31600), and 316L (UNS S31603) are the most commonly specified materials for this application. These grades offer excellent general corrosion resistance, good formability, and reliable performance across a wide temperature range.
- Super Austenitic Stainless Steel (超级奥氏体不锈钢) — Grades such as 904L (UNS N08904) and Duplex 2205 (UNS S31803) may be specified for applications involving aggressive chemical environments or elevated temperature/pressure conditions.
- Heat-Resistant Stainless Steel (耐热不锈钢) — Grades such as 310S (UNS S31008) are available for extreme temperature applications exceeding 800°C.
Key Material Properties
| Property | Specification (Grade 304) | Specification (Grade 316L) | Specification (Duplex 2205) |
|---|---|---|---|
| Tensile Strength (抗拉强度) | ≥ 515 MPa | ≥ 485 MPa | ≥ 550 MPa |
| Yield Strength (屈服强度) | ≥ 205 MPa | ≥ 170 MPa | ≥ 450 MPa |
| Elongation (伸长率) | ≥ 40% | ≥ 40% | ≥ 25% |
| Operating Temperature Range (使用温度范围) | -196°C to +870°C | -196°C to +870°C | -50°C to +350°C |
| Chloride Pitting Resistance (氯化物点蚀抗力) | Good | Excellent | Excellent |
| Corrosion Resistance (耐蚀性) | Good in atmospheric and mild chemical environments | Superior in chloride-containing and marine environments | Excellent in high-chloride and high-stress environments |
| Thermal Conductivity (热导率) | 16.3 W/(m·K) | 16.3 W/(m·K) | 17.4 W/(m·K) |
| Weldability (可焊性) | Excellent | Excellent | Good (requires appropriate filler metal) |
Chemical Composition (Typical)
| Element | 304 (UNS S30400) | 316L (UNS S31603) | 2205 (UNS S31803) |
|---|---|---|---|
| Carbon (C) | ≤ 0.08% | ≤ 0.03% | ≤ 0.03% |
| Chromium (Cr) | 18.0 – 20.0% | 16.0 – 18.0% | 22.0 – 23.0% |
| Nickel (Ni) | 8.0 – 10.5% | 10.0 – 14.0% | 4.5 – 6.5% |
| Molybdenum (Mo) | — | 2.0 – 3.0% | 3.0 – 3.5% |
| Nitrogen (N) | — | — | 0.14 – 0.20% |
| Sulfur (S) | ≤ 0.03% | ≤ 0.03% | ≤ 0.02% |
Product Specifications
Dimensional Specifications (尺寸规格)
| Parameter | Specification / Range | Standard Reference |
|---|---|---|
| Outer Diameter (外径, OD) | Φ6 mm – Φ32 mm (standard); up to Φ51 mm (custom) | GB/T 12771, ASTM A269 |
| Wall Thickness (壁厚, WT) | 0.5 mm – 4.0 mm | GB/T 12771, ASTM A213 |
| Coil Inner Diameter (盘管内径, CID) | Φ100 mm – Φ500 mm (customizable) | Manufacturer Specification |
| Coil Length (盘管长度) | 5 m – 500 m (configurable per project requirement) | Project-Specific |
| Coil Pitch (盘管间距) | 10 mm – 50 mm (adjustable based on heat transfer requirements) | Project-Specific |
| Surface Finish (表面状态) | Bright Annealed (BA), Pickled & Passivated (酸洗钝化), Mirror Polish (抛光) | ASTM A270, GB/T 4237 |
| End Form (端部形式) | Plain Cut, Beveled, Threaded, Flanged, or Custom Fitting | Per Customer Drawing |
| Tolerance — OD (外径公差) | ±0.1 mm to ±0.5 mm (depending on diameter) | ASTM A269, GB/T 12771 |
| Tolerance — Wall Thickness (壁厚公差) | ±10% (standard); ±5% (precision grade) | ASTM A269, GB/T 12771 |
Pressure & Thermal Performance
| Performance Parameter | Specification |
|---|---|
| Maximum Working Pressure (最大工作压力) | Up to 1.6 MPa (standard); up to 4.0 MPa (high-pressure grade) |
| Hydrostatic Test Pressure (水压试验压力) | 1.5 × Maximum Working Pressure |
| Maximum Heating Medium Temperature (加热介质最高温度) | 250°C (hot water); 350°C (steam) |
| Heat Transfer Efficiency (换热效率) | ≥ 90% (optimized coil geometry) |
| Thermal Expansion Coefficient (热膨胀系数) | 16 × 10⁻⁶ /°C (304/316L); 17 × 10⁻⁶ /°C (2205) |
Standards & Compliance
| Standard | Description |
|---|---|
| GB/T 12771 | Stainless Steel Seamless Tubes for General Application (中国国家标准) |
| ASTM A269 | Welded Austenitic Stainless Steel Tube for Chemical and General Applications |
| ASTM A213 | Seamless Austenitic Stainless Steel and Heat-Resisting Alloy Tubing for Boilers, Heaters, and Similar Uses |
| ASTM A270 | General Requirements for Stainless Steel Tubing, Welded and Unwelded |
| GB/T 4237 | Stainless Steel Plates, Sheets, and Strips (中国国家标准) |
| ASME B31.3 | Process Piping Code (for pressure-containing applications) |
| EN 10216-5 | Technical Delivery Conditions for Seamless Stainless Steel Tubes for Pressure Purposes |
Manufacturing Process
The production of the Stainless Steel Heating Coil Tube follows a rigorous multi-stage manufacturing process to ensure dimensional accuracy, material integrity, and long-term service reliability:
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Raw Material Selection & Inspection (原材料选择与检验)
Premium-grade stainless steel billets or coils are sourced from certified suppliers. Incoming material undergoes spectroscopic analysis (光谱分析) to verify chemical composition compliance with specified grade requirements. Certificates of Material Origin (COC/材质证明) are reviewed and archived.
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Pipe Forming (制管成型)
Depending on the production method, the tube is formed via either Seamless Extrusion (无缝挤压) or Welded Coil Forming (焊接盘管成型). For seamless tubes, the billet is heated and extruded through a die to produce a continuous tube. For welded tubes, precision-cut stainless steel strip is rolled and formed into a tubular shape.
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Welding & Seam Formation (焊接与焊缝形成)
For welded tube configurations, the longitudinal seam is joined using Automatic Argon Arc Welding (TIG, Tungsten Inert Gas Welding / 钨极氩弧焊) or High-Frequency Resistance Welding (高频电阻焊). The weld seam is subsequently ground and polished to achieve a smooth internal and external surface, minimizing flow resistance and stress concentration points.
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Coil Forming & Bending (盘管成型与弯曲)
The straight tube is fed through a precision Coil Winding Machine (盘管绕制机) equipped with CNC-controlled bending dies. The coil geometry — including pitch, diameter, and total length — is programmed according to the specific project requirements. The bending process is performed at controlled speeds to prevent material deformation, wall thinning, or ovality (椭圆度) exceeding acceptable tolerances.
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Heat Treatment & Annealing (热处理与退火)
Post-forming, the coil tube undergoes Solution Annealing (固溶退火) at temperatures typically between 1010°C and 1150°C, followed by rapid quenching (in air or water). This process relieves residual stresses introduced during forming, restores the austenitic microstructure, and maximizes corrosion resistance and ductility. For Grade 316L and Duplex 2205, careful control of the cooling rate is essential to prevent sensitization (敏化) and intergranular corrosion (晶间腐蚀).
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Surface Treatment — Pickling & Passivation (表面酸洗与钝化)
The coil tube is subjected to Acid Pickling (酸洗) using a mixture of nitric acid and hydrofluoric acid to remove oxide scales and surface contaminants. This is followed by Passivation Treatment (钝化处理), which establishes a thin, stable chromium oxide (Cr₂O₃) passive film on the surface, providing enhanced corrosion resistance. The passivation process is verified using the Blue Spot